Cross-Reference to Related U.S. patent applications
U.S. patent applications Ser. Nos. 879 411, filed May 6, 1992, now U.S. Pat. No. 5,194,546, and 888,998, filed May 26, 1992, now U.S. Pat. No. 5,206,322, by the same inventors as herein, and assigned to the same assignee, described and claimed the starting material used in this invention.
1. Field of the Invention
This invention relates to crosslinked PVP, and, more particularly, to a method of crosslinking a stable, crosslinkable PVP solution by changing the pH of the solution.
2 Description of the Prior Art
Merijan, in U.S. Pat. No. 3,563,968, described the preparation of functional graft homopolymers of vinyl lactams, e.g. vinyl pyrrolidone, by reaction of polyvinylpyrrolidone with allyl amine or allyl alcohol in ethanol solvent in a bomb reactor at 130.degree.-140.degree.C.
Kitchell, in U.S. Pat. Nos. 4,692,328 and 4,772,484, disclosed the chemical crosslinking reaction of functional graft homopolymers of vinyl pyrrolidone with glutaraldehyde to form a gel which was useful in biological applications. Polyvinylpyrrolidone (PVP) and PVP copolymers also have been crosslinked physically using E-beam or gamma radiation.
However, it would be of advantage to provide a simple method of crosslinking a stable, crosslinkable vinyl lactam polymer, at a predetermined pH, without requiring further condensation with a glutaraldehyde, or the use of expensive radiation equipment.